Safety device for a top boom pivotally mounted on a crane boom

ABSTRACT

A safety device for a top boom pivotally mounted on a main boom of a crane, in which a first control system arranged on the top boom of the crane includes an angle indicator, a power indicator, a rated value indicator and a comparing device, and in which a second control system arranged on the main boom or the crane upper structure includes a source of constant current and a decoding device. The first and second control systems are electrically connected to each other only by one conductor and the mass of the main boom and of the top boom.

United States Patent [191 Gerdes et al.

[ 1 Sept. 3, 1974 1 SAFETY DEVICE FOR A TOP BOOM PIVOTALLY MOUNTED ON A CRANE BOOM [75] Inventors: Werner Gerties, Langendamm; Otto Kiister, lsums, both of Germany [73] Assignee: Fried. Krupp Gesellschaft mit beschrankter Haftung, Essen,

Germany 22 Filed: Apr. 20, 1973 21 Appl. No.: 353,138

[52] US. Cl. 212/39 R, 340/267 C [51] Int. Cl G08b 21/00, B66c 13/16 [58] Field of Search"; 212/39 A, 39 R, 39 MS; L 340/267 C [56] References Cited .UNITED STATES PATENTS 3,139,988 7/1964 Brekelbaum et al.....

2/1971 Linke ..340/282X 3,566,386 2/1971 Hamilton 212/39 A 3,641,551 2/1'972 Sterner et al. 212/39 R X 3,710,368 7 H1973 Hamilton 340/267 C 3,740,534 6/1973 'Kezer et al. 212/39 A X Primary Examiner-Even C. Blunk Assistant Examiner-JamesL Rowland Attorney, Agent, or Firm-Walter Becker [57] ABSTRACT A safety device for a top boom pivotally mounted on a main boom of a crane, in which a first control systern arranged on the top boom of the crane includes an angle indicator, a power indicator, a rated value indicator and a comparing device, and in which a second control system arranged on the main boom or the crane upper structure includesv a source of constant 5 Claims, 2 Drawing Figures SAFETY DEVICE FOR A TOP BOOM PIVOTALLY MOUNTED ON A CRANE BOOM The present invention relates to a safety device for a top boom pivotally mounted on a crane boom.

It is an object of the present invention to provide a safety device which will eliminate the dangers inherent to the employment of a top boom pivotally mounted on a crane boom, especially when the top-boom is provided at one end of a telescopically designed boom of a mobile crane, and which will be as inexpensive as possible.

tion will appear more clearly from the following specification in connection with the accompanying drawing, in which:

FIG. 1 diagrammatically illustrates a side view of a portion of the rotatable platform of a mobile crane with a telscopic boom and a top boom.

FIG. 2 shows a controlcircuit for the safety device according to the invention.

The safety device according to the present invention is characterized primarily in that a first part of the safety device, arranged at the top boom and comprising an angle indicator, a power indicator, a rated value indicator and a comparing device, and a second part of the device, arranged on the main boom or crane upper structure and comprising a source of constant current and a decoder, are connected to each other only by one conductor while the mass of the crane boom and of the top boom are connected to each other as feeding and return conductors.

Referring now to the drawing in detail, it will be seen from FIG. 1 that on the platform 1 of the upper structure of a mobile crane, which upper structure is rotatable about a vertical axis, there is mounted a main boom 2. This main boom 2 is journalled in bearings 3 and is by means of a hydraulic pivoting device 4 adjustable as to height. The movable parts of the telescopic boom 2 are designated with the reference numerals 5, 6, 7. To the outer end of the outermost telescopic part 7 there is. connected one end of a length indicator cable 8. This cable 8 has one end wound upon a tensioning drum 9 which is mounted on the main boom 2. A traction motor continuously tends to turn the tensioning drum 9 in such a way that the cable 8 will be wound up as far as possible. Consequently, the cable 8 will in all positions of the displaceable telescopic parts 5, 6, 7 be taut. The revolutions of drum 9 during the outward and inward movement of the telescopic parts 5, 6, 7 are measured and'are employed for ascertaining the length of the telescopic boom for a non-illustrated device for limiting the loadmoment of the crane.

At the tip of the outermost telescopic-part 7 there is pivotally mounted the top boom 10 which is journalled in a joint 11 and has a pivot axis which is parallel to the axis of the bearing 3. The top boom 10 is engaged by a neck pulling cable 12 which is passed to a winch drum 13 on the main boom 2. At the tip of the top boom 10 there are provided reversing rollers 14 for the cable of the crane hoisting mechanism 15. The weight of the re; spective load Q suspended on the last mentioned cable is ascertained by means of a power indicator 16 which is arranged on the top boom 10. In' FIG. 1, the power indicator 16 is diagrammatically indicated as a stroke indicator which measures the displacement of two parts These and other objects and advantages of the inven- The safety device according to the invention and illustrated in FIG. 2 comprises two parts, namely parts I and II, of which thepart I is provided on the top boom 10 whereas the part II is provided on the main boom 2 or on the crane upper structure. Both parts I and II are electrically interconnected only by the length indicating cable 8 and by the mass of the crane boom consisting of the parts 2, 5, 6 and 7 and of the top boom 10. Cable 8 and mass 18 represent the feeding and return conductor.

Part II comprises a voltage source 19 which supplies the safety device with the necessary energy. Connected to the voltage source 19 is a source 20 of constant current. The circuit comprising the voltage source 19 and the constant current source 20 consists of a conductor 21 in the part II; thecable 8 a conductor 22 in the part I which has interposed therein a constant voltage regulator 23, a potentiometer 24 pertainingto the angle indicator 17, and an Ohmic resistor 25; as well asthe return conductor through the mass 18'.

Part I also includesa' rated value indicator 26 which through a conductor 27 is connected to the source 23 of constant voltage. By means of a switch 28 it is possible in the rated value indicator 26 to make effective various load curves for the employment of differently long top booms. The angles a ascertained by the angle indicator 17 are conveyed to the rated value indicator 26. The respective rated values of the permissible power Q acting upon the top boom, which rated values have been ascertained by the rated value indicator 26, are conveyed to the comparing device 29. This device 29 contains the respective actual values of the load Switch 36 is adapted to be closed by means of a relay 39 connected to the comparing device 29 when the weight of the load Q as ascertained by the power indicator 16 reaches the rated value determined by the rated value indicator26; Switch-37 will be closed when the angle indicator 17 indicates that the angle a is zero, in other words, when the top boom 10 has been lowered to its horizontalpo sition. Switch 38 is a strokelimit switch. This switch 38 will be' closed when the load suspended on cablelS has reached its highest permissible position and the hook fittings abut anabutment 40.

The length indicating cable 8 and the conductor 22 are connected to each other by a disconnecting switch 41 which is normally closed and which will be opened when the top boom has been pivoted into a highest permissible position, in other words, when the angle a has reached its maximum value.

Part II of the safety device according to the invention comprises a decoder 42 which is supplied with energy by the voltage source 19 through a conductor 43, and through a conductor 44 is connected to the conductor 21. The decoder 42 has an outlet 45 from which pulses for generating warning signals and for switching off the drives of the winch drum 13 and of the crane hoisting mechanism are emitted in case of overloads, when lowering the top boom to the horizontal position, when the limit switch 38 is actuated and when a short-circuit-oc-' curs between the cable 8 and the mass 18. A second outlet 46 of the decoder 42 furnishes pulses for turning off the above mentioned drives when the top boom is lifted to its highest permissible position or when the cable 8 breaks.

Part II of the safety device furthermore comprises a device 47 for indicating the respective angle a. This device 47 is by a conductor 48 connected to a conductor 21 and is supplied with energy from the voltage source 19 through a conductor 49. Furthermore the device 47 is through the conductor 50 connected to the outlet or exit 46 of the decoder 42.

As long as the switches 36, 37 and 38 are in open condition, while the switch 41 is closed, the respective angles a are indicated by the device 47. This is due to the fact that the potentiometer 24 of the angle indicator 17 will, depending on the various angular positions of the top boom 10, with constant intensity of the current passing through the conductors 21, 22 and the cable 8 furnish different voltages to the indicating device 47. I

When the load Q suspended on cable 15, the weight of which is ascertained by the. power indicator 16, reaches the rated value as it is furnished by the rated value indicator 26 for the respective angle a ascer-. tained by the angle indicator 24, switch 36 will be closed by the relay 39. Thereby the potentiometer of the angle indicator 24 and the resistor 25 are shortcircuited with regard to mass 18. The resulting voltage drop at the decoder 42 will through the outlet 45 bring about a warning signal and will also bring about that the crane drives will be switched off This will also take place when the potentiometer 24 of the angle indicator and the resistor 25 are short-circuited by closing the. switches 37 or 38 because the top boom has then been lowered to the horizontal plane or the load has been lifted until the hook fittings abut the abutment 40. If the cable 8, for instance due to damage to the insulating supports by means of which it is held on the telescopic parts 5, 6, 7, comes into conductive connection with the mass 18 of these parts, a voltage drop will likewise result at the decoder 42. Also in this instance through the outlet45 a warning signal is released and the respective crane drives will be turned off.

When the top boom 10 is pivoted into its highest per- 'missible position, switch 41 opens. Accordingly, the

voltage at the decoder rises and through outlet 46 a warning signal is released and the drive for the winch drum 13 is turned off. This will also occur when cable 8 should break.

Cable 8 thus serves a plurality of purposes. On the one hand, it serves for the load moment limiting device of the crane for ascertaining the length of the telescopic boom. On the other hand, cable 8 transmits to the indicating device 47 the voltages which correspond to the different angular positions of the top boom 10. Furthermore, by the cable 8 the decrease and increase in voltage becomes effective on the decoder, which decrease and increase occur at the mentioned limit condi 4 tions in view of the closing of switches 36, 37, 38 and the opening of switch 41.

The invention may also be employed whenthe top which are ascertained at the top boom are transmitted and a top boom pivotally connected to said main boom,

by a single conductor to that point where they act upon the signalling device. Such single conductor may with a crane equipped with a telescopic boom be formed by a length'indicating cable which is necessary for the load moment limitation. In this way additional transmitting means will no longer be required. Precautionary measures are taken in a simple manner in case the conductor should break or a short-circuit should occur between the conductor and the mass of the boom.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawing but also comprises any modifications within the scope of the appended claims.

What we claim is: 1.In combination with a crane having a main boom a safety device which includes:

a. a first control system arranged on said top boom and comprising: I

b. a means for measuring the actual angle formed by said top boom with a horizontal plane;

c. a means for measuring the actual load suspended on said top boom;

d. a means for supplying the rated values of the load permissible to be suspended on said top boom, this means being tuned by said means for measuring the actual angle; i I

e. a comparing device comparing the values received from said means for measuring the actual load suspended on said top boom with the values received from said means for supplying the rated 'values of the load permissible to be suspended on said top boom;

f. a second control system arranged on a part of said crane other than said top boom and comprising:

g. a source of constant current;

h. a decoder electrically connected to said source of constant current for receiving energy therefrom and being operable to emit pulses for generating operative-warning signals;

i. an angle indicator electrically connected to said source of constant current for receiving energy therefrom and indicating the antual angle formed by said top boom with a horizontal plane;

k. a first conductor interconnecting said first and said second control systems:' a l 1. said first conductor on the one hand being connected to a second conductor within said first control system which second conductor is connected to the mass of said top boom and said main boom through a potentiometer tuned by said means for measuring the actual angle and through a resistor arranged in series with said potentiometer;

m a first branch conductor branching off fromsaid second conductor and being connected to said mass and including a first switch means which normally is open, but under the influence of said comparing device is closed to short-circuit said potentiometer and said resistor when the value received by said comparing device from said means for measuring the actual load suspended on said top boom reaches the value received by said comparing device from said means for supplying the rated values of the load permissible to be suspended on said top boom;

n. a second branch conductor branching off from said second conductor and being connected to said mass and including a second switch means which normally is open, but under the influence of said means for measuring the actual angle is closed to short-circuit said potentiometer and said resistor when the top boom has lowered to the horizontal plane;

0. said first conductor on the other hand being connected to a third conductor within the second control system and through said third conductor and through said constant current source to said mass.

2. A safety device according to claim 1, in which a third branch conductor branching off from said second conductor is connected to the mass of said top boom and said main boom and includes a third switch means which normally is open, but under the influence of an 6 abutment is closed to short-circuit said potentiometer and said resistor when the load suspended on said top boom has reached its highest permissible position.

3. A safety device according to claim 1, in which a fourth switch means is arranged in series with said first conductor means which normally is closed, but under the influence of said means for measuring the actual angle formed by said top boom with a horizontal plane is opened when said top boom has reached its-highest which said first conductor is the length indicator cable of a device for limiting the load moment taking effect to the crane.

I UiIITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No v3, 5 I September 1974* Dated Inventor(s W m G I'deS t 31 It is qe t tifie d that errqr appears in the abOve-ide-ritified patent and that sa idiglget'ters Paitent -ere hereby cox rected as shgwn below "5 D Fer e -iig n Apfilicatibn Priority Dat v v I l- 9 ermany -,----222 .152 7.o

. sig edg grici- 10th ay flpgcembe a i974.

(SEAL) Attest: I I I v I v MCCOYM. GIB ON 31R, f c; MARSHALL DANN Attesting'officer g I Commissioner qfPatente F ORM PO-! 050 (10-69) I USCOMM- DC 60376'P69 u.s.' eovznuuiwr rum-nus OFFICE: 9. 930 

1. In combination with a crane having a main boom and a top boom pivotally connected to said main boom, a safety device which includes: a. a first control system arranged on said top boom and comprising: b. a means for measuring the actual angle formed by said top boom with a horizontal plane; c. a means for measuring the actual load suspended on said top boom; d. a means for supplying the rated values of the load permissible to be suspended on said top boom, this means being tuned by said means for measuring the actual angle; e. a comparing device comparing the values received from said means for measuring the actual load suspended on said top boom with the values received from said means for supplying the rated values of the load permissible to be suspended on said top boom; f. a second control system arranged on a part of said crane other than said top boom and comprising: g. a source of constant current; h. a decoder electrically connected to said source of constant current for receiving energy therefrom and being operable to emit pulses for generating operative-warning signals; i. an angle indicator electrically connected to said source of constant current for receiving energy therefrom and indicating the antual angle formed by said top boom with a horizontal plane; k. a first conductor interconnecting said first and said second control systems: l. said first conductor on the one hand being connected to a second conductor within said first control system which second conductor is connected to the mass of said top boom and said main boom through a potentiometer tuned by said means for measuring the actual angle and through a resistor arranged in series with said potentiometer; m. a first branch conductor branching off from said second conductor and being connected to said mass and including a first switch means which normally is open, but under the influence of said comparing device is closed to short-circuit said potentiometer and said resistor when the value received by said comparing device from said means for measuring the actual load suspended on said top boom reaches the value received by said comparing device from said means for supplying the rated values of the load permissible to be suspended on said top boom; n. a second branch conductor branching off from said second conductor and being connected to said mass and including a second switch means which normally is open, but under the influence of said means for measuring the actual angle is closed to short-circuit said potentiometer and said resistor when the top boom has lowered to the horizontal plane; o. said first conductor on the other hand being connected to a third conductor within the second control system and through said third conductor and through said constant current source to said mass.
 2. A safety device according to claim 1, in which a third branch conductor branching off from said second conductor is connected to the mass of said top boom and said main boom and includes a third switch means which normally is open, but under the influence of an abutment is closed to short-circuit said potentiometer and said resistor when the load suspended on said top boom has reached its highest permissible position.
 3. A safety device according to claim 1, in which a fourth switch means is arranged in series with said first conductor means which normally is closeD, but under the influence of said means for measuring the actual angle formed by said top boom with a horizontal plane is opened when said top boom has reached its highest permissible position.
 4. A safety device according to claim 1, in which a source of constant voltage is arranged in said second conductor and is operable to supply energy to said means for measuring the actual load suspended on said top boom further to said means for supplying the rated values of the load permissible to be suspended on said top boom and further to said comparing device.
 5. A safety device according to claim 1, in which said main boom includes a basic part and at least one telescopic part said parts interengaging each other, and in which said first conductor is the length indicator cable of a device for limiting the load moment taking effect to the crane. 